Messages are called for in many situations where speech cannot be used or can be used only with difficulty. A few examples are as follows: areas where noise levels are very high; areas where silence is preferred or in zero noise areas, such as in the military, during test taking or during church services; construction areas such as high buildings or in sewers where the voice cannot be heard clearly; boat to boat communications; and between swimmers or between a swimmer and a boat in underwater activity.
Computers have not been associated with portable, or hand-held, sign technology partly because monitor viewing screens are dominated by the fluorescent screen associated with the cathode ray tube (CRT) technology, which has until recently been bulky. Miniaturized microprocessor technology has recently allowed reduction of CRT monitors with displays that are as crisp and readable as laser printing on paper.
Computer display technology is presently used with displays that are based upon the well-known liquid crystal display (LCD), such as are used for messages displayed on the screens of bank cash vending machines. LCDs could be used in operative association with miniaturized microprocessor technology.
The same miniaturized technology has reduced motherboard processors so that an entire package including display and microprocessor is reduced to fit into a shirt pocket, that is to say, to the rectangular dimensions of a credit card. Such advances in miniaturized microprocessor technology can be applied as well to keyboard processors.